1. Field of the Invention
The present invention relates to a construction and a method for the manufacture of an optical path changing device for optically coupling parts having optoelectronic converting components, optical waveguides, etc., arranged two-dimensionally.
2. Description of the Related Art
In recent years, the development of optical interconnections for signal transmission inside devices at high density is being pursued vigorously with the aim of developing massively parallel computers for parallel signal processing between high-speed, high-capacity optical communication systems, large numbers of processors, etc. When performing optical interconnections of this kind, processing of transmitted optical signals is carried out by electronic devices. In the interface devices connecting these electronic devices, hybrid optical-electrical devices are required in which optical waveguides, optoelectronic converting components, large-scale integrated circuits (LSIs), switches, etc., for electronic control, or electric circuits for driving electronic components are combined. In order to achieve high-speed broadband communication systems, in particular, the demand for devices provided with optoelectronic converting components such as vertical-cavity surface-emitting lasers (VCSELs), laser diodes (LDs), photo diodes (PDs), etc., has risen.
To meet this kind of demand, techniques have been proposed such as “Ninety-degree Optical Path Changing Techniques in Optical Circuit Packaging”, Journal of Japan Institute of Electronics Packaging, Vol. 2, No. 5, pp. 368-372, 1999, for example, in which an optoelectronic converting component and an optical printed circuit board are optically coupled by disposing an optical pin with a micromirror on the optoelectronic converting component, disposing a through hole having a similar shape to the optical pin in the optical printed circuit board, and inserting the optical pin into the through hole.
In this conventional 90-degree optical path changing technique in optical circuit packaging, as shown in FIG. 17, a core 2 constituting an optical waveguide is embedded in an optical printed circuit board 1, a through hole 3 is formed in the optical printed circuit board 1 so as to cut across the core 2, and a micromirrored optical pin 5 fixed to an optoelectronic converting component 4 is inserted into the through hole 3. The through hole 3 is formed into the optical printed circuit board 1 such that an aperture center thereof is perpendicular to an optical axis of the core 2, and a tip surface of the optical pin 5 is formed into a micromirror 5a having an angle of 45 degrees to the optical axis. Thus, for example, light propagating through the core 2 is totally reflected by the micromirror 5a, is directed into the optical pin 5, propagates inside the optical pin 5, and reaches the optoelectronic converting component 4. In other words, the core 2 and the optoelectronic converting component 4 are optically coupled by 90-degree optical path changing.
By adopting this conventional optical path changing technique, degradation of optical coupling between light-emitting components and the optical waveguide, optical coupling between the optical waveguide and light-detecting components, etc., resulting from light emitted from the light-emitting components into free space or light emitted from the optical waveguide into free space having an angle of radiation and spreading, can be prevented. In addition, using this conventional optical path changing technique is advantageous in that optical coupling between the optoelectronic converting component 4 and the core 2 can be performed by a like construction in cases where light is inserted into the core 2 from a light-emitting component (an optoelectronic converting component) such as a VCSEL, etc., through the micromirror 5a, and also in cases where light is emitted from the core 2 into a light-detecting component (an optoelectronic converting component) such as a PD, etc.
However, because the conventional optical path changing technique is constructed in the above manner, micromirrored optical pins 5 must be secured to each of the optoelectronic converting components 4 separately, making the manufacturing process complicated and preventing cost reductions from being achieved.
Furthermore, it is necessary to form a through hole 3 in the optical printed circuit board 1 in order to insert the optical pin 5. Since this optical pin 5 has a diameter of several μm to several hundred μm and the through hole 3 must be formed so as to have a diameter equivalent to the optical pin 5, machining of the through hole 3 is extremely difficult, making the rate of production poor. This problem becomes more pronounced as the number of through holes 3 is increased. In addition, it is difficult to form the inner wall surfaces of the minute through hole 3 without irregularities, leading to deterioration of optical coupling efficiency between the core 2 and the optical pin 5 as a result of irregularities at the end surface of the core 2 formed by the through hole 3.
In a construction in which the optoelectronic converting components 4 are arranged two-dimensionally, optical pins 5 must be fixed to large numbers of optoelectronic converting components 4 separately, making positioning accuracy of the optical pins 5 poor. Thus, optical axis misalignment may occur between the optoelectronic converting component 4 and the optical pin 5, giving rise to deterioration in the optical coupling efficiency.
In a construction in which a large number of layers in which cores 2 are arranged two-dimensionally, in order to cape with increases in the number of optoelectronic converting components 4, the lengths of the optical pins 5 differ in each core layer, making long optical pins 5 necessary. This lengthening of the optical pins 5 may give rise to buckling in the optical pins 5, making the positioning accuracy of the micromirrors 5a relative to the optical axes of the cores 2 poor, thereby causing the optical coupling efficiency to deteriorate.